KIMMERIDGIAN DINOSAURS. 569 



111 Hylaosaurus we find the nearest approach to Omosaurus in the proportion of the 

 length of the humerus giving attachment to the great tuberous crests from the radial and 

 ulnar sides of its proximal part. But in the Isle of Wight specimens referred, with doubt, 

 to that Dinosaur, the radial crest is more strongly, and, in reference to its Saurian nature, 

 more typically twisted palmad than in the huger Kimmeridgian genus. It shows a 

 tuberous thickening anconad of its distal end, in the place of the ridge, d', fig- 2, 

 PI. 70, in Omosaurus. 



Radius. — This antibrachial bone in Omosaurus (ib., figs. 7 — 11) has a subcom- 

 pressed shaft, expanding moderately and almost equally into the two articular ends, as 

 far as their degree of conservation shows; but it is probable that the more mutilated 

 distal end (fig. 10) when entire would give a somewhat greater breadth than the proximal 

 one or ' head.' This (ib., fig. 9) is of a narrow subelliptic shape. A small part of the 

 concave articular surface, a, for the radial condyle of the humerus, is preserved. The 

 anconal surface of the shaft (fig. 7) is feebly divided at its distal two thirds into two 

 facets by a low rising, hardly to be called a ridge, beginning at the middle of that 

 surface at its proximal third and inclining as it descends toward the radial border of 

 the distal end. The concavity of both borders, and especially of the ulnar one, narrows 

 transversely the shaft, but this preserves more equably its ancono-palmar thickness (see 

 the section of the middle of the shaft in fig. 11). The lateral facet (fig. 8, h) at the 

 proximal end for articulation with the ulna is more convex than is usual in Bcpiilia. 



The surface (ib., fig. 8, e) for the insertion of the biceps tendon is well defined. The 

 thenal prominence (ib., figs. 8 and 10, /) extending or deepening the cup, y, for the 

 scaphoid, is strongly developed, and is thicker than usual, as far as it is preserved. Its 

 outer surface is roughened, as if for the ligamentous attachment of some bone, such sur- 

 face extending to the angle, y (fig. 8), at the broadest part of the distal end of the radius. 



Ulna. — The proximal extension of the articular cup (PI. 70, fig. 13, „) upon an 

 anconal or olecranal production marks this bone as sti'ongly as in Varanus (ib., fig. 15, a) 

 but the excavation (p) of the shaft below the proximal end is differently situated. It 

 Avould seem as if the ulnar or outer border of that depression in Varanus (ib., fig. 15) 

 had been moved or extended palmad, in Omosaurus, toward the narrower, palmar, surface 

 of the bone ; and to such an extent that part of this excavation comes into view from the 

 ulnar side, as at c, fig. 14. This excavation is continiied distad for more than half the 

 length of the bone {c,c'). Below this part the shaft assumes a subtriedral form; and 

 its anconal border bends toward that aspect as it approaches the carpus. The articular 

 surface for this segment of the fore limb is wholly destroyed. 



Manus. — Of the carpal bones have been extracted a left scaphoid, left cuneiform, 

 and left unciform. Of these three large wrist-bones the scaphoid is the smallest, as in 



